1. Field of the Invention
The invention relates to a method for manufacturing a syntactic sleeve for insulating a pipeline.
2. Description of the Prior Art
Syntactic materials consist of a polymeric matrix material in which hollow glass or other microspheres of different sizes and densities are embedded. A number of the physical properties of syntactic materials appear to be dependent on the size and distribution of the microspheres in the matrix material. For example the heat insulation coefficient of the syntactic material increases with an increasing content of microspheres whereas the mechanical stress at failure of the syntactic material decreases with an increasing content of microspheres.
Syntactic materials are particularly suitable for insulating subsea pipelines for transport of oil and gas in view of their high creep resistance in comparison to other heat insulating materials such as formed polymers. However, the mechanical loads exerted to the insulation material during pipelaying operations are extremely high, and the mechanical strength thus required leads to a low microsphere content which again leads to a low heat insulation coefficient and the requirement of thick insulation layer.
The presence of a thick insulation layer is of particular concern during pipelaying operations which are usually carried out by a reel large or J-lay installation technique during which the pipe is subject to extremely high bending and tension forces since an increased thickness leads to a corresponding increase of elongation and compression at the outer circumference of the insulating layer and an increased risk of formation of cracks in the insulation material.
Thus there still is a need for an improved syntactic pipeline insulation system which has a high heat insulation coefficient and which has simultaneously a high ductility, in particular near the outer circumference of the insulation layer.
It is therefore an object of the present invention to provide a method for manufacturing a syntactic insulation layer around a pipeline which meets the above need.